1. Field of the Invention
The present invention relates to a four poles circuit breaker, and more particularly, to a power transmission mechanism for the four poles circuit breaker.
2. Description of the Conventional Art
A four poles circuit breaker (namely, 3-phases 4-lines type circuit breaker) has a configuration comprising four movable contactors and stationary contactors corresponding to four poles, respectively, to switch 3-phase alternate current supply lines having R-pole (namely, R-phase), S-pole (namely, S-phase), and T-pole (namely, T-phase), and a neutral line having a neutral pole (N-pole or namely N-phase) grounded to the earth at the same time. Here, the neutral line is a line performing a very important role to safely supply electric power. It is because various relays for detecting an abnormal current caused by ground-fault current, short-circuit current, lightning, and the like, are connected and installed to a neutral line and a plurality of ground lines for stabilizing 3-phase voltage are also connected to the neutral line in order to prevent the damage of load devices from occurring or prevent a local electrical accident from being spread to a large range area.
Accordingly, in such a four poles circuit breaker, it is required to have a so called “fast closing and late opening” characteristic in which the movable contactor of a neutral pole is brought into contact with the corresponding stationary contactor earlier than the movable contactor of other poles in the meaning of first securing the ground when switching to a closing position, namely, to the ON position, and the movable contactor of a neutral pole is separated from the corresponding stationary contactor later than the movable contactor of other poles in the meaning of implementing circuit opening in a state that the ground is secured when switching to a trip position (opening position) of the circuit breaker.
For the fast closing and late opening characteristic, there has been proposed a configuration that the movable contactor of a neutral pole is disposed more close to the stationary contactor than the movable contactor of other poles (other three poles excluding the neutral pole) according to the related art. However, according to the related art, it may have a so called fast closing and late opening characteristic, but have a problem that electrical insulation of the neutral pole cannot be secured since the opening distance (namely, insulation distance) between the stationary contactor and the movable contactor in a neutral pole is shorter than the opening distance of other poles when opening the circuit.